just moments ago, president obama spoke to the nation about the attack. the president says there is are plenty of unanswered questions in this tragedy. >> what we don't yet know, however, is who carried out this attack or why, whether it was planned and executed by aer toistic organization -- an organization or an individual or individuals. >> just a short while ago, the flag at the white house was lowered to half staff in honor of the boston marathon victims. three people were killed, including an 8-year-old boy. more than 170 were wounded. today is also the 6th anniversary of the virginia tech shooting massacre. on april 16th, 2007, a gunman shot and killed 32 people on that campus before he killed hill self. earlier this morning, there was a moment of i vens held in virginia. it was followed by the ringing of the bell for each victim of the shooting. the governor of virginia declared today, virginia tech remembrance today. >>> the san jose mercury news is selling its long-time headquarters in silicon valley. they own 36 acres. it's been at that locatio